The present invention relates generally to the preparation of fluoride crystals, and particularly to making of barium fluoride crystals with improved below 175 nm wavelength optical properties.
More specifically, said invention relates:
to a process of preparing barium fluoride crystals, which is improved with reference to the purity of the crystals prepared with a permeable graphite crucible; and
to a process of preparing barium fluoride crystals in permeable graphite crucibles with the resulting barium fluoride crystals having an increased transmission in the far-ultraviolet (λ<170 nm) at about the 157 nm wavelength of the fluorine excimer laser output.